Obturating firing-pin



J. T. THOMPSON.

OBTURATING FIRING PIN.

IIIIIIIIIIIII LED MAR 25 I 1,345,565. Pat nt d July 6, 1920.

UNITED STATES PATENT OFFICE.

JOHN T. THOMPSON, OF'N'EWPORT, KENTUCKY, ASSIGNOR OF ONE-HALF TO THOMAS E. RYAN, OF NEW YORK, N. Y.

OBTURATING FIRING-PIN.

Application filed March 25,

To all whom it may concern:

Be it known that I, JOHN T. THOMPSON, a citizen of the United States, and resident of Newport, in the county of Campbell and State of Kentucky, have invented new and useful Improvements in Obturating Firing- Pins, of which the following is a speclfication.

My invention relates to firing pins for guns and more particularly to firing pins formed to prevent the escape of the gases of explosion through the passage in which the pin operates.

While my invention is particularly adapted for use in guns of the type using caseless cartridges or separate loading ammunition of types where the powder charge is not qontained in the, usual cartridge or casing, it is nevertheless of utility in connection with the usual type of fixed ammunition since often a certain amount of gas escapes around the primer.

With the usual type of firing pin or striker in use on rifles and machine guns no attempt is made to provide means for preventing escape of gas around the firing pin into the bolt. The opening on the bolt face is usually somewhat larger than the firing point and affords a ready passage for any gases which appear at that point. That there is considerable escape of such gases is evidenced by the foul condition in which a bolt assembly is found when dismantled for cleaning after firing. This fouling of the bolt and firing mechanism is detrimental to the gun and where sustained fire is maintained for considerable time, without opportunity for cleaning, the mechanism may become so fouled as to jam. Even before jamming occurs the fouling often slows up the mechanism to an appreciable extent.

Passage of the gas into the bolt or firing mechanism has a further deleterious effect in that it heats these parts to a high temperature and carbonizes the lubricants, thus increasing the wear of the parts. This gas which is not only at a high temperature but is under heavy pressure and moving at great velocity, has the effect of eroding the metal with Which it contacts. This erosion is particularly detrimental to the parts in a bolt or in a gun firing mechanism where the several parts require a nicety of fit in order to properly function and even a slight erosion may have a marked effect on the efficiency of the pieceor may even cause a Specification of Letters Patent.

Patented July 6,1920.

1920. Serial No. 368,646.

passage of gases into the bolt or firing mechanism through the firing pin channel. It is also an object to provide a firing pin which will accomplish this result whether in its fully extended or in its retracted position or in any intermediate position. It is another object to provide a pin which will accomplish these results without modification of any of the gun structure other than of the firing pin itself. It is a further object to provide a pin of the character described which is automatic in its action, simple in construction and relatively inexpensive in manufacture. Other and further objects will appear as the description proceeds.

Broadly considered, my improved firing pin comprises an extended central portion adapted to fire the primer of the cartridge and a circumferential lip adapted to closely fit the firing pin channel and to be forced into intimate contact with that channel by the powder pressure.

I have illustrated several preferred embodiments of my invention in the accompanying drawings, in which Figure 1 is a broken away longitudinal section showing my firing pin in the breach of a gun;

Fig. 2 is a longitudinal section of a bolt head having a modified form of firing pin;

Fig. 3 is a view similar to Fig. 2 showing another modification;

Fig. 4 is a view similar to Fig. 2 of an additional modification; and i Fig. 5 is a view showing a modification of the firing pin shown in Fig. 1..

In Fig. 1, 6 designates the barrel of a gun, 7 the breech housing and 8 the bolt head. These parts have been shown in a diagrammatic manner and per s-(a form no part of the present invention. The firing pin shown in Fig. 1 has the central extended point 11 surrounded by the circular depression 12, the outer edge of which forms the lip 13 which is in close contact with the inner sarface of the firing pin channel 14:.

The pin shown in Fig. 2 has the extended point 15 surrounded by the sleeve 16 which latter, as shown, is screwed on the firing pin proper at 17. In the form shown in Fig. 3,

the head of the pin is recessed forming the thin circumferential lip 18 and the striker 19 is screwed in the center in the base of the depression.

The forms of pins shown in Figs. 1 and 5 require a modification of the firing pin channel in the bolt. As shown in Fig. 4, the channel in the bolt 9 has the undercut interior lip 20 which coacts with the circumferential lip 21 on the firing pin. The striker 22 is threaded into an axial recess in the pin. In Fig. 5 the bolt 10 has the interior lip 23 similar to the lip 20 of Fig. 4, and it coacts with the lip 24 on the firing pin. The face of the pin is formed similar to the pin shown in Fig. 1.

All of the forms of pin which I have shown have a central portion adapted to extend beyond the face of the bolt and fire the primer and have this central projection surrounded by a circumferential portion closely fitting the channel walls and so formed that gas pressure against the pin will urge this latter portion into intimate contact with the channel.

Gases exert a thrust normal to the wall of the confining vessel and in the form shown in Fig. 1 the gases normal to the curve of the lip 13 will urge it radially outwardly against the bolt. Similarly the gases will urge outward the sleeve 16 of Fig. 2 and the lip 18 of Fig. 3.

In the form shown in Fig. 4, a double gaslock is effected, the gases urging the lip 20 into contact with the lip 21 and urging the latter lip into contact with the channel wall.

In Fig. 5 the pin acts as does that of Fig. 1, the additional lips 23 and 2 1 serving to prevent escape of gases which may pass between the pin and bolt and further serving to prevent the pin passing so far forward as to permit the lip 12 to extend beyond the face of the bolt, in which case there would be gas pressure on both the inner and outer faces of the lip and the obturation would hence be imperfect.

Obviously, the proportions of the several elements of my firing pin may be varied without departing from myinvention, and the forms shown in .Figs. 2, 8 and f may be made integral ifdesired rather than in two pieces as shown. My pin is entirely inde- 1 pendent of the type of gun upon which it is used.

I have shown several forms of myimproved obturating firing pin but all have in common the fact that the obturation is automatically secured by the powder pressure, and the greater the pressure the more intimately and firmly is the pin held in contact with the channel in which it operates. Even should the axially operating thrust due to the pressure force the firing pin back into the channel, the obturation will nevertheless take place with its fullefiiciency.

I claim:

1. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a portion thereof adapted to be urged into intimate contact with the walls of the channel by powder pressures in the chamber.

2. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a portion thereof adapted to be urged substantially radially into intimate contact with the walls of the channel by powder pressures in the chamber.

3. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a circumferential lip portion thereof adapted to be urged into intimate contact with the walls of the channel by powder pressures in the chamber.

4. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a portion thereof adapted to be pressed into intimate contact with the channel wall, the degree of pressure being dependent upon the powder pressure in the chamber.

5. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a portion adapted to extend into the chamber, and a circumferential lip portion adapted to contact with the walls of the channel.

6. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a portion adapted to extend into the chamber, and a circumferential lip portion adapted to contact with the walls of the channel, the surface of the circumfcrential portion which is adjacent the chamber being so situated that powder pressure thereon causes the lip to be pressed sub stantially radially against the firing pin channel.

7. In a gun, a firing pin entering the chamber thereof through a firing pin channel, the pin having a portion adapted to extend into the chamber, a circumferential lip portion adapted to contact with the walls of the channel, and the channel having an internal undercut lip adapted to coact with the lip on the firing pin.

8. A. firing pin for guns having a head provided with an extended central portion, and a circumferential lip adapted to be pressed radially outward by pressure thereon normal to its interior surface.

9. A firing pin for guns, having a head provided with an extended central portion, a recessed portion surrounding the extended portion, and a circumferential lip surrounding the recessed portion, the lip being of less hei ht than the extended central portion.

igned by me at New York, N. Y., this seventeenth day of March, 1920.

JOHN T. THOMPSON. 

